Insulation Question

[dogwood]

Does anyone know at what point you are no longer reaping much benefit from adding R-value to a wall or ceiling. At what R-value are you reaching the point of diminishing return? There was a previous post where it was stated that when spray foaming your boiler's storage tank you'd get little additional insulation value past three inches of foam. I thought maybe there's an analogous figure for wall and ceiling insulation, possibly dependent on how far north you are.

I will be framing and insulating my new boiler room hopefully shortly, as well as increasing ceiling insulation throughout the house so would appreciate any advice. I will probably spray foam my 1000 gallon tank too with the recommended three inches of foam, if I can find someone who will spray with high temperature rated foam.

Mike

 

[Frozen Canuck]

Depends entirely on the insulation material being used. Fiberglass gets worse as temperature drops (lower R value than rated) closed cell foams get better as temperature drops (higher R value than rated). As far as diminishing returns are concerned, cost of energy to heat is going one way....up. Cost of insulation is fixed at the price you pay upon purchase. I guess when you reach the point where you can heat a building simply by putting people into it your probably safe to stop insulating as there will be no further benefit in continuing. Trust me that would be in excess of R 200 so unless you are close to that....keep on insulating.

 

[dogwood]

I was thinking of the pink fiberglass kind.

Mike

 

[Frozen Canuck]

Simple rule.....nothing will give you as rapid an ROI as insulation....so as much as you can fit in....or as much as your budget will allow....don't forget to keep all soffit vents clear as the attic will need to breathe no matter how much insulation you put in.

 

[Frozen Canuck]

Forgot to mention that you can blow in cellulose in your attic (a lot less crawling around compared to laying more fiberglass batts). Way less itch too.

 

[Fred61]

IMHO You can't beat cellulose insulation for tha attic. NO JOINTS!

 

[coolidge]

You might have seen this report before, if not take a look as long as it comes through. For your tank you will not find a high temp foam, the company might say it is but they are full of sh%t. Polyurethane foam is polyurethane foam, it all has the same burning charecteristics. I did spray three inches on my tank(all but about an 18 inch strip to heat the basement) working great. As far as diminishing returns, should be around 5" foam in the roof and 3" in the walls. Cellulose is second with as much as your budget will allow and fiberglass should be hauled to the landfill right from the factory. I have been doing some expirements with Roxul with good results so far, not as good as foam but. www.sprayfoam.com/cnt/docs/ORNL_FiberglassReport.pdf

 

[dogwood]

Thanks for the link to the study Coolidge. Disheartening. Non-withstanding I will need to roll out more pink insulation on top of what I already have. That's because it will be covering most of my electical, gas, plumbing, and other runs, and I may need to roll it back out of the way as need be. I was wondering if I add another R-30 of the fiberglass to the existing R-30, will I now have twice the amount of heat retention from the insulation? Or is it more like the spray foam which as described in the previous thread only adds marginal insulation value after a certain point. Is there a point of diminishing return for pink fiberglass insulation as well, is what I am trying to find out.

On a different note Coolidge, you mentioned you have spray foamed your storage tank, although you did think the claims of high temp resistant spray foam were bogus. I'm confused. Have you or anyone else had problems with high temp failure of their spray foam insulation on their storage vessels that would warn me off spraying mine. Or have those of you who have sprayed yours have good reports. I'm assuming my storage tank will get into the 190's degree range at times. Has anyone used the high temp foams described in previous threads and if so with what result. Maybe going with loose fill for the 1000 gallon pressurized tank would be a safer bet.

Mike

 

[tom in maine]

I think as of today, R-60 is a goal that is reasonable.
The number changes with fuel costs.

When you get into this realm, windows and doors are now a real killer, contributing well over 1/2 the heat load
for an average house, so an investment in windows that are over R-5 and/or window insulation makes good sense.

Most of our house is R-65 or higher--all foam insulation.
If I was building new, I would use SIPS panels.
They are a great deal.

 

[Fred61]

You might have seen this report before, if not take a look as long as it comes through. For your tank you will not find a high temp foam, the company might say it is but they are full of sh%t. Polyurethane foam is polyurethane foam, it all has the same burning charecteristics. I did spray three inches on my tank(all but about an 18 inch strip to heat the basement) working great. As far as diminishing returns, should be around 5" foam in the roof and 3" in the walls. Cellulose is second with as much as your budget will allow and fiberglass should be hauled to the landfill right from the factory. I have been doing some expirements with Roxul with good results so far, not as good as foam but. www.sprayfoam.com/cnt/docs/ORNL_FiberglassReport.pdf

http://www.sprayfoam.com/mnps/fullthread.cfm?threadid=8245&mnforumid=2&mnboardid=5&startat=1

 

[dogwood]

Great link Fred61. I think the idea of spray foam charring in the 200 degree range has scared me sufficiently. Thanks so much for the heads up. Looks like blown in insulation for the tank. I'll look for the older posts on how much and what kind to use. Wonder what kinds of temps blown in insulation can safely withstand.

Mike

 

[Fred61]

I got these links (the one in my previous post and the one below) on foam insulation last summer from a friend of a friend who is in the spray foam business when I balked at the price to foam my tank. Sorry I didn't share them with you sooner. Both are quite educational. I had a hectic summer with the rework of my house, trying to tear off a roof and install new trusses in between rain drops.

http://www.betterfoam.com/Products/SprayFoamInsulation/tabid/107/Default.aspx

 

[dogwood]

Thanks again Fred. They do list a couple of foam packages that are rated up 240 degrees, interesting but pricey too as you say. Hope your new roof and trusses turned out okay. That's a lot of work you've done. Hope you had some help.

Mike

 

[Como]

Usually windows have the worst pay back.

Too many people seem deluded into replacing perfectly good, serviceable windows which can be upgraded with systems that will end up being worse.

 

[dogwood]

Windows, Anderson Slimline, vinyl clad, double hung, have been in eighteen years and are going nowhere. just put in some replacement 4x6 Pella casement windows to replace fixed windows in the kitchen. They're here to stay too. Don't recall the R-(or U)value although they are Low-E, double paned, and nicely constructed. Got the nine 3'x6' double hungs at a salvage yard, brand new with screens and grilles at half price ($150 per), when building. What a score. Need to find some bargain R-30 and R-15 rolls now. Thanks for your input.

Mike

 

[DaveBP]

The trouble with the "point of diminishing returns" is that it isn't a point. It's just a continually decreasing payback as you continue to add more insulation. Every person's (or business's) criteria are different. I call it the fog of diminishing returns.

I went so far as to make an Excel spreadsheet to roughly calculate the heat loss of my house when I was designing it. Not a very precise heat loss calculator, mind you, just a heat loss comparison. But the graph could show me how much lower the heat bill would change if I added more insulation to the wall or windows.

My dilemma was that the 3 largest rooms had south facing window walls, 250 sq.ft. Even double pane, Low-E, krypton filled glass is a poor heat retainer at night compared to a simple 4" wall filled with fiberglass. So much of the walls of these rooms are glass that adding more than the R25 to R30 insulation to the walls will not save me much heat. My wife hates insulation panels on windows so that is out of consideration.

My compromise was to leave it at R30 (max) and know that if I want to lower my heat bill in the future it will mean insulating the windows, not the walls.

I framed my attic so it could hold as much as 24" of blown in insulation without blocking the soffit vents. It has 16" of cellulose now and I can add more later very easily.

I came into several very good deals on fiberglass and urethane rigid panels so I went with that. The foamed-in stud method would be appealing if I could amortize it in a home builder loan but I am building my place on a cash basis. It was just too much money up front to me when I had a couple bids done on the urethane.

 

[Piker]

Thanks for the link to the study Coolidge. Disheartening. Non-withstanding I will need to roll out more pink insulation on top of what I already have. That's because it will be covering most of my electical, gas, plumbing, and other runs, and I may need to roll it back out of the way as need be. I was wondering if I add another R-30 of the fiberglass to the existing R-30, will I now have twice the amount of heat retention from the insulation? Or is it more like the spray foam which as described in the previous thread only adds marginal insulation value after a certain point. Is there a point of diminishing return for pink fiberglass insulation as well, is what I am trying to find out.

On a different note Coolidge, you mentioned you have spray foamed your storage tank, although you did think the claims of high temp resistant spray foam were bogus. I'm confused. Have you or anyone else had problems with high temp failure of their spray foam insulation on their storage vessels that would warn me off spraying mine. Or have those of you who have sprayed yours have good reports. I'm assuming my storage tank will get into the 190's degree range at times. Has anyone used the high temp foams described in previous threads and if so with what result. Maybe going with loose fill for the 1000 gallon pressurized tank would be a safer bet.

Mike

Despite the fear that seems to arise about using spray foam in hydronic applications... I have yet to actually see any of the closed cell polyurethane spray foam fail under NORMAL operating temperatures. I have had our thermal storage tanks to 205 many times with no visible signs of any degradation of the foam whatsoever. I did bring the tanks up to a little over 100* F before we sprayed them to get them at least partly expanded in an attempt to prevent cracking and to help the first layer of foam expand a little better. So far so good. I would recommend it to anyone... though this is not to say that there are not other viable options. For us, it was a no-brainer... dark, somewhat damp crawlspace, with limited space ruled out just about everything else.

cheers

 

[dogwood]

Piker, I would really like to spray foam my tank like yours. I wonder why you're not having any problems with failure or charring as the first link Fred61 provided indicated you should be? I'll look again into the local availability of a high temp resistant spray foam like Fred61's second link described. I admire the efficiency of your foamed tank in retaining heat and would like to replicate it. On the other hand I can't chance charring and potential fire hazard.

DaveBP, appreciate your cash as you go approach with it's limitations and rewards. I did it the same way or would have put in lots more insulation initially as well. Only have an inch and a half under the slab due to the prohibitive cost at the time. Thought it wouldn't be a big issue with the then lower energy costs and living as far south as Virginia. My mistake. Hopefully getting the ceiling up to R-60 and upstairs walls up to R-26 will help mitigate this miscalculation, along with installing our Solo Innova. Hate to be burning extra wood indefinitely to make up for the underslab insulation misjudgement and not using SIPs but there it is. I'll make sure not to block the soffit vents too. I'm curious, what did your spreadsheet tell you the optimum insulation levels would be for your home if cost were no object?

Mike

 

[Piker]

Piker, I would really like to spray foam my tank like yours. I wonder why your not having any problems with failure or charring as the first link Fred61 provided indicated you should be? I'll look again into the local availability of a high temp resistant spray foam like Fred61's second link described. I admire the efficiency of your foamed tank in retaining heat and would like to replicate it. On the other hand I can't chance charring and potential fire hazard.

Mike

Well, I am by no means a Spray foam expert... but I believe the foam that was sprayed on our tanks was rated at 240* or 250*... not 100% sure if it was fire rated foam or not. Areas where the supply piping has overspray stuck to it show no discoloration of the foam. I would think that an area with overspray, where you are able to see the foam closest to the pipe, would show the most "charring" if it was going to charr. I would also think that if I had reached the foams flashpoint where it began giving off any vapors, that those vapors would a) have an odor (maybe?) and b) push the outer foam away from the tank and cause cracks. I have not experienced either.

If the foam were going to be exposed to open flame, I might reconsider... but otherwise I feel pretty safe. The contractor had no safety concerns when he did the job, and he's been doing sprayfoam for a while now.

cheers

 

[dogwood]

Piker, it seems it boils down to whether the local spray foam contractors have that high temp foam rated at 240-250 degrees like you were able to get. I'll call around. Maybe it's not uncommon. I just don't know. As you can tell I've no experience with spray foam other than what comes out of the small cans of it you get at Lowes. I do like quality work and I'd prefer to do it the way you have if at all possible. Good idea about having the tank heated a bit before spraying too. Thank you much.

Mike

 

[DaveBP]

DaveBP, appreciate your cash as you go approach with it’s limitations and rewards. I did it the same way or would have put in lots more insulation initially as well. Only have an inch and a half under the slab due to the prohibitive cost at the time. Thought it wouldn’t be a big issue with the then lower energy costs and living as far south as Virginia. My mistake. Hopefully getting the ceiling up to R-60 and upstairs walls up to R-26 will help mitigate this miscalculation, along with installing our Solo Innova. Hate to be burning extra wood indefinitely to make up for the underslab insulation misjudgement and not using SIPs but there it is. I’ll make sure not to block the soffit vents too. I’m curious, what did your spreadsheet tell you the optimum insulation levels would be for your home if cost were no object?

If cost were no object, I'd fill the stud bays with as much spray foam as they would hold. But even then, the wooden studs start to be the greatest path of heat loss through the walls and you can't stop that unless you double/stagger-stud the walls or put rigid foam over the whole surface of the wall. This is where the SIPs are to the greatest advantage.
It isn't just cost. At some point extra insulation won't stop other heat losses that were trivial before. Check out the habitations they build for the Antarctic colonies. Very low heat loss but I wouldn't want to live like that.

1-1/2" foam under the slab doesn't sound like a bad compromise to me where you are.

I think it's hard to beat concentrating on air infiltration. It's a bigger factor than most people can believe in total heat loss.

If you are air-conditioned in summer you have a whole lot of other factors we don't deal with as much up here in the "cool, cool, North".

At some point you just have to take your financial machete out and make an ending and live with it.

It's always a compromise.

 

[Frozen Canuck]

You are right Dave one always has to make compromises otherwise your house cost will rival well....the casinos of Vegas. BTW on the subject of cost, I just found a SIP manufacturer who will make me panels that use the foam in the size (thickness) he receives it.....48" thick, I have no idea on the R value of 48" of closed cell foam or the cost, frankly I was scared to ask about cost. Info like that gets me to thinking though. First thought: where am I going to find a customer with pockets that deep? Second thought: we do 9" nominal panels with a 4 person crew & a crane; how many more people do I need to handle panels 48" thick? Top & bottom plate that's easy 2 layers of 3/4" plywood. Let's see...walls thick enough for a daybed/seating area in all windows, well maybe not in kitchen/bathroom. Yes lot's of ideas come to mind. Including how does one afford this? GARN BARN ANYONE???? :lol: :lol: :lol:

 

[dogwood]

Dave, I did consider the double staggering of the studs option at the time too. Didn't want to get on the wrong side of the inspectors, so decided to go with 2x8 studs to provide the semblance of using traditional building techniques. This is a traditional area. We do have central air conditioning for the summer. You're right about air infiltration losses too. Reminds me that I've noticed drafts around exteriors doors I'll need to seal. The drafts were not there when the doors were new eighteen years ago. Always something to keep on top of.

Mike

 

[coolidge]

Sorry, been running wy as@ of for the last couple days. Eveything thats been posted here is very good info. I have had my tank to 230 degrees (by mistake) and have had no foam failures yet. My supply and return pipes are covered with about four inches, no problems. I would just use the regular 2lb foam your local contractor has "on the shelf". You may also want to cover the foam with an approved 15 minute thermal barrier required by law, but this could be done by you the homeowner. www.painttoprotect.com

This will satisfy any code official. Hope this helps.

 

[DaveBP]

Please allow me to spew a bit here. I think this "charring" is a red herring on this forum. We're talking about boiling water temps not exhaust flue temps.

I don't remember if it was stated on that other forum that was linked here but I assume that wood kiln was heated with hot air. If any charring happened it might have been on that duct from the heat source. If the kiln temp was 190 who knows what the supply air duct temp was, and what temp it hit when something went a little overboard to cause them to look for damage. It all just strikes me as the sort of unintentional disinformation that becomes "common knowledge" on the internet. Too many people have used normal off-the-shelf urethane for this sort of application for at least these few years not to have some first hand reports of deterioration, let alone "charring".

There. Now I feel better. Thank you for indulging me.

P.S. If you want a first hand report of the bogeyman, watch out for carpenter ants where foam (styrene or urethane/polyisocyanurate) is moist. I had a mixed stack of rigid panels under evergreen shade that was not covered from rain that was all tunneled through up to 3 feet off the ground. They absolutely LOVE warm moist foam. They just tunnel down to where their favorite temp is.

If I had an outdoor storage tank insulated with spray foam I would parge it with one of those cement/fiber/acrylic binder products for coating exposed foam around foundations.
Parge-All is a brand I have used. There are epoxy/fiber/sand products as well for those with a more generous budget.